Refrigerating apparatus with defrosting controls



Aug 1961 J. J. PREOTLE ETAL 2,994,207

REFRIGERATING APPARATUS WITH DEFROSTING CONTROLS Filed Feb. 25, 1959 4 Sheets-Sheet 1 74 Fl. I we .INVENTORS John J. Preol/e Charles 5. Rambo/0' The/r A/fo ney 1961 J. J. PREOTLE ETAL 2,994,207

REFRIGERATING APPARATUS WITH DEFROSTING CONTROLS Filed Feb. 25, 1959 4 Sheets-Sheet 2 I 49 INVENTORS John J. Preof/e BY Char/es E. Rqmbo/d The/r Alf nay Aug. 1, 1961 J. J. PREOTLE ET AL REFRIGERATING APPARATUS WITH DEFROSTING CONTROLS Filed Feb. 25,. 1959 4 Sheets-Sheet 3 INVENTORS John J. Preot/e By Charles E. Rambo/d gg g ,4

Their Af/orey Aug. 1, 1961 J. J. PREOTLE ET AL 2,994,207

REFRIGERATING APPARATUS WITH DEFROSTING CONTROLS Filed Feb. 25, 1959 4 Sheets Sheet 4 Fig. .9

JNVENTORS Fig. 7 John J. Preof/e BY Char/es E. Rambo/a flw w The/r Alfomey the sides and top of the door opening. The back United States Patent C REFRIGERATING APPARATUS WITH DEFROST- ING CONTROLS John J. Preotle and Charles E. Rembold, Dayton, Ohio,

assignors to General Motors Corporation, Detroit,

Mich., a corporation of Delaware Filed Feb. 25, 1959, Ser. No. 795,443 4 Claims. (Cl. 62-155) This invention pertains to refrigerating apparatus and more particularly to frost-proof upright freezers.

In upright freezers it has been customary to store the frozen articles and packages on refrigerated shelves main tained at below F. This keeps the articles and packages amply cold by direct conduction. However, frost accumulates on the shelves and packages, eventually in objectional amounts. This frost must either be laboriously scraped 01f or all the articles and packages removed to another freezer and the entire refrigerator defrosted completely. Either of these methods can be such a nuisance as to cause adverse customer reaction to increased sales of such a freezer.

It is an object of this invention to provide an upright freezer in which satisfactory refrigerating temperatures are maintained without interruption for required defrostmg.

It is another object of this invention to provide an upright freezer in which the evaporator is outside the freezing compartment, and the freezing compartment is kept at satisfactory temperatures throughout by a uniform lateral flow of air between the shelves, which air has been adequately cooled by the evaporator.

It is another object of this invention to so arrange the cold air refrigeration distribution circuit that the articles and packages stored on the shelves will not obstruct the circulation in such a way as to prevent uniform temperature maintenance.

It is another object of this invention to provide an upright freezer cooled by cold air in such a manner that articles and packages therein are uniformly cooled regardless of their quantity and distribution.

These and other objects are attained in the form of upright freezer shown in the drawings in which a perforated air inlet duct is provided in a hollow wall portion adjacent the sides and top of the door opening which extends downwardly to an evaporator chamber beneath the freezing compartment containing a cross-fin evaporator insulated from the freezing compartment. Air is drawn through the evaporator by a centrifugal fan and discharged upwardly through a vertical duct and lateral branch horizontal ducts directly beneath the rear edges of'the shelves into the freezing compartment. The air flows horizontally forwardly over the top of the articles and packages stored on the shelves and also beneath the shelves back to the perforated air duct extending around of each of the shelves is provided with a guard preventing anyone from placing articles or packages directly in front of the air inlet openings. Since it is practically impossible to completely fill the space between these shelves, there will always be sufiicient space between the shelves to permit the forward horizontal air circulation within the freezing compartment. The fan is stopped during the electric heat defrosting of the evaporator retaining the cold air surrounding the articles and packages until refrigeration is resumed.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a-preferred embodiment of the present invention is clearly shown.

In the drawings:

FIGURE 1 is a vertical transverse sectional view taken along the lines 1-1 of FIGURES 2 and 3 illustrating one form of my invention;

FIGURE 2 is a front view with the door open, half of which is broken away to show the ductwork on the back of the rear wall of the inner liner;

FIGURE 3 is a horizontal sectional view taken along the line 3-4 of FIGURE 2;

FIGURE 4 is a wiring diagram for the freezer;

FIGURE 5 is a fragmentary cross sectional view illustrating the interfitting of the breaker strip and the front edge of the inner liner and the perforated plastic duct;

FIGURE 6 is a plan view of the blower housing heater;

FIGURE 7 is a side view of a shelf and shelf front;

FIGURE 8 is a fragmentary vertical section of the drain trap and drain heater; and

FIGURE 9 is a fragmentary vertical sectional view taken along the line 9-9 showing the accumulator plate and its connections.

Referring now to the drawings, the cabinet is provided with a box-shaped metal outer shell 20 provided with an irregular lower wall 22 beneath which is a machine compartment 24. The cabinet also includes plane side walls 26 and 28 and a plane top wall 30. Within the outer shell is a metal inner liner provided with a rear wall 32 having horizontal perforated inlet openings 34 adjacent to but slightly beneath the rear edge of the shelves 40 as well as an additional inlet 36 directly beneath the top wall 38. Beneath the lowermost shelf 40 is a wire basket 41 having the sides of its upper rim 43 slidably mounted in plastic channels 45 on the side walls 52. The shelves 40 are formed of a perimeter wire member upon which are fastened bars extending from the front to the rear. According to this invention the air inlets 34 are each shielded and protected by the horizontal bars 42 and 44 supported by arc-shaped wire projections 46 extending downwardly and rearwardly from the perimeter wire of each shelf 40, as shown in FIGURE 1. The air inlets 36 are screened with perforated metal or wire mesh. The shelves 40 are supported by shelf pegs 48 upon the side walls 52 of the inner liner and the projections extending into holes or recesses in rear wall 32.

The air is drawn from the front of the inner liner through the perforations into return air duct 54 provided by a bulge 56 in the top 38 and sides 52 of the inner liner and by plastic molding strips 58 having the uniformly spaced horizontal slots or perforations 60. The rear portion of this perforated molding strip 58 is bevelled or extends at about a 45 angle and is retained in the retaining groove 62 provided by a V-shaped metal strip welded to the sides 52 and the top of the inner liner, as shown in FIGURES 1 and 3. The front edge of this molding strip 58 is received in a rearwardly facing notch in the breaker strip 64'. The breaker strip 64 also has an outwardly facing notch which fits over the in-turned front edge of the sides 52 and the top 38 of the inner liner member, as shown in FIGURES l, 3 and 5. The breaker strip 64 has a large irregular tubular portion fitting into a large channel-shaped retainer member provided by forming a channel at the inside of the front edge of the outer shell, as shown in FIGURES 1 and 3.

The duct 54 extends downwardly along the sidewalls 52 and opens into the evaporator compartment 66 provided beneath the bottom wall 68 of the inner liner. The bottom wall includes a front horizontal portion, an intermediate, slightly inclined portion and a very steep rear portion. The bottom of the evaporator compartment 66 is provided by a horizontal grooved member 70 in which the grooves extend to a drain trough 72, from which a drain sleeve 74 extends downwardly into the machine compartment 24 and is provided with an internal trap 76 (FIGURE 8) within the drain-pan 78.

The drain sleeve 74 of molded plastic is tapered from top to bottom and has an outwardly extending flange 273 at the top which rests upon the recessed edge of the drain portion 72. The sleeve 74 has an enlarged portion 275 at the point at which it extends through the opening in the metal wall 277 forming the bottom face of the lower wall 22. The sleeve 74 i prevented from moving upward- 1y by the spring metal retaining washer 279. The internal trap 76 is formed within the sleeve '74 by a thimbleshaped plastic member 281 having holes 282 at the bottom and an outwardly extending lower flange. Within the thimble member 281 is a tube 283 also having an outwardly extending lower flange. The sleeve 74 has a lower outwardly extending flange of the same diameter as the enlarged portion 275 and the flanges of the thimble member 281 and the tube 283 all of which are held in position concentrically by the removable elastomeric bottom member 285 having an outlet aperture concentric with the tube 283 and having an in-turned upper flange 287 extending around and over the flange at the bottom of the sleeve 7 4.

The defrost water flows from the drain portion 72 down through the sleeve 74 through the holes 282 to the top of the tube 283. The top of the tube 283 maintains the liquid level in the trap 76 high enough to prevent the water from being drawn through the trap by the powerful suction of the fan 94. The water overflows through the tube 283 and the opening in the bottom member 285. The thimble member 281 and the tube 283 may be removed readily for cleaning and inspection by pulling or prying the in-turned flange 287 off the flange at the bottom of the sleeve 74. The sleeve 74 may be removed from the evaporator compartment by removing the spring retaining washer 279.

The drain-pan 78 preferably rests upon or is located above the super heat remover coil 80 connected to a sealed motor-compressor unit 82. The evaporator compartment 66 is provided with a front wall 85 sealed to the bottom Wall 78 at its lower edge and sealed to the breaker strip 64 at its upper edge. The evaporator 84 is of the vertical fin, horizontal cross-tube type and rests on the bottom wall '70. It is insulated from the bottom wall 68 of the inner liner by a thin slab of rigid foam insulation 86. The upper and lower edges of the fins of the evaporator 84 are notched to receive the upper and lower electric heaters 87 and 88 of the sheathed tubular type.

The rear wall 90 of the evaporator compartment 66 is provided with an opening 92 concentric with the cen trifugal fan 94 driven by the electric motor 96 extending through an opening in the rear wall 98 of the cabinet shell 20. The centrifugal fan 94 is surrounded by a shroud 121 of a suitable plastic having an integral rearwardly extending cylindrical flange 123 extending through the opening in the rear wall 98 and provided with suitable supports 125 for the fan motor 96. The cylindrical flange 123 has Within it a cylindrical-shaped piece 127 of foam insulation. The fan housing 121 contains a small flexible electric heater 129 (see FIGURES l and 6). The drain portion 72 also includes a small flexible electric heater 131. These heaters 129 and 131 are either connected in series or in parallel with the defrost heaters 87 and 88 so that all areenergized during defrosting. The fan motor 96 is stopped during the energization of the 1 electric heaters 88, 129 and 131 so that the cold air remains within the inner liner to keep cold the articles and packages upon the shelves 40 and in the basket 41.

The fan 94 draws air from the duct 54 into the evaporator compartment, through the evaporator 84 and the opening 92 and discharges the air through the fan housing or shroud 121 to a plastic or metal symmetrical duct 133 provided upon the rear wall 32 of the inner liner. This duct includes vertical portions 135, 137, 139 and 141 of 4 gradually reducing width and cross-section between which are the laterally extending branches 143 extending on opposite sides directly behind the air inlet openings 36. The duct 133 also includes the vertical partitions 134, 136 and 138 which provide a separate passage for half of each branch 143 excepting the top branch. The fan 94 forces the air, cooled to a temperature below 0 F. by the evaporator 84, through the vertical portions -141 and the branches 143 and the openings 36 into the interior of the inner liner for horizontal flow between the shelves 40 and beneath the top wall 38 over and around the frozen articles and packages on the shelves 40 to the apertures 60 providing access to thedownwardly extending duct 54.

This arrangement prevents frost formation within the inner liner since frost always tends to collect at the coldest point in the circulation system which is the evaporator 84. Any frost which temporarily is formed at other points in the circulation system will be sublimed by the air circulation and carried to.the evaporator 84.

Upon the wall 90 at one side of the opening 92 is an accumulator and connector plate 151 having a suction line connection 153 with the compressor 82. Within the suction line and suction line connection 153 there extends a capillary tube 155 extending from the outlet of the condenser 147 mounted on the rear wall 98. .This capillary tube 155 extends through the T-shaped passage arrangement 157 to a passage portion 159 of reduced cross-section within which it fits snugly. This passage portion 159 connects to the outlet connection 161 connecting to the inlet of the evaporator 84. The outlet of the evaporator 84 connects to the connection 163 at the bottom of the accumulator portion 165 extending upwardly at an angle of about 40. The top of this accumulator portion 165 is connected by a downwardly extending passage 167 to the T-connection 157 through which the evaporated refrigerant flows outside the capillary tube 155 to the connection 153 and the suction line to the inlet of the compressor 82.

As shown in FIGURE 4, a defrost timer 169-has one terminal connected by the conductor 171 to one supply conductor 173. This defrost timer 169 has a connection 175 to the thermostat switch 179 connecting to compressor motor 82 and through a connection 177 to the fan motor 96. Themotor 82 is connected by a conductor 83 to the supply conductor 183. The snap acting adjustable thermostatic control switch 179 has a thermostat bulb 181 mounted upon the rear lower return bend of the evaporator 84 as shown in FIGURE 1. The thermostat 179 cycles both the motors 82 and 96.

Within the defrost timer 1 69 is a timer motor 321 con nected between the conductor 171 and a conductor 323 connecting with the other supply conductor 183. Normally the double-throw switch 325 within the timer provides a connection between the conductors 171 and 175 to the thermostatic switch 179 and the motors 82 and 96. Once every twenty-four hours, the timer motor 321 moves the double-throw-switch 325 to its alternate lower position providing a connection between the conductors 171 and 185. This energizes the defrost heaters 87', 88, 129 and 131. These heaters are connected through the defrost limiter switch 187 to the other supply conductor 183. This defrost limiter switch 187 is located upon the drain-pan 70 behind the evaporator 84 adjacent its right side. This defrost limiter switch 187 is calibrated to open at some suitable temperature, such as 50 F. which is the minimum temperature calculated to insure complete defrosting of the evaporator 84 as well 38011181 parts of the evaporator compartment 66. When thi: defrost limiter switch 187 opens, it energizes a shun circuit including the conductors 327 and 329 betweer which there is a solenoid coil 331 located in the defros timer 169. 'This solenoid 331 when energized return; the double-throw switch 325 to its normal refrigerating position- This'upper position will energize the motorc'ompressor unit to resume refrigeration.

After such a defrost period, it will take a considerable time before the evaporator 84 is brought down to below freezing temperatures and particularly to the temperatures below the temperatures normally maintained in the storage compartment. For this reason, it is desired to delay the operation of the fan motor until the evaporator 84 reaches the normal low operating temperature. This is done by connecting the second terminal of the fan motor through the conductor 333 to the defrost limiter switch ,187which is open after each defrost cycle for a considerable period after reaching the maximum defrost temperature of-SO" F. at which it has deenergized the defrost heaters87, 88, 131 and 129. The differential of the defrost limiter switch, that is, the difference between 50 F. and the low temperature of 22 F. at which it recloses, therefore is the principal factor in determining the time at which this switch will reclose and the time delay before permitting the enengization of the fan motor 96. By varying the differential of this thermostat 187, the time delay in restarting the fan motor 96 can be varied.

An orange neon signal light 189 is connected between the supply conductor 183 and a normally closed thermostatic switch 191 also connected to the supply conductor 173. This switch 191 is located in the return air duct 54 between the second and third shelves 40. The light 189 is located in the center of the removable panel 149 and remains lighted as long as the thermostatic switch 191 remains below 22 F. to indicate safe operation. Extinguishing of the light 189 for any reason indicates possible damage to the contents of the freezer and calls for immediate attention.

From time to time, such as once every twenty-four hours, the electric heaters 87, 88, 129 and 13 1 are energized by the defrost timer 169 while the refrigerating system and the fan 94 are idle to rapidly melt the frost from the evaporator 84 and cause the melted frost to flow down the drain 74 and through the trap 76 into the drain-pan 78 from which the melted frost water will gradually evaporate due to the heat from the super heat coil 80 and the sealed motor-compressor unit 82. This defrosting takes place with sutficient rapidity that the articles and packages stored within the inner liner are kept by the cold air at a safe temperature throughout the defrosting period. The insulating slab 86 of foam insulation prevents the heat from the defrost heater 88 from being transmitted to the bottom wall 68 of the inner liner.

The space between the inner liner and the outer shell is preferably filled with a foamed plastic insulation of high insulating value. A front door 145 likewise insulated with a foamed plastic insulation of high insulating value closes the front opening of the inner liner. This door 145 is provided with wire shelves 146 having straight bottoms and straight wire guards with the ends of each protruding into the thickened portions. The condenser 147 is provided on the rear wall 98. The sealed unit '82, the super heat remover coil 80, the condenser 147 and the evaporator 84 are connected together into an operative refrigerant circuit to liquefy the refrigerant in a conventional manner. The machinery compartment is closed at the front by a removable panel 149. The air distribution system thus insures proper cooling at all times without interruption and defrosting is accomplished automatically without requiring any attention from the user. Packages and articles, when removed, are free of frost.

The shelves 40 each have a vertical bracket 210 (see FIGURE 7) at each front corner each provided with a set of vertically spaced buttons 212 and 214. Each button 212 is received within an arcuate slot 216 in a bracket 218 provided upon the ends of each shelf front 220. Each button 214 is received in a vertical slot 222 in the bracket 218. The shelf fronts 220 are held locked in their vertical position as shown in FIGURES 1 and 7 by having the tops of the slots 216 and 222 resting upon the buttons 212 and 214. To lower the fronts 220, they are raised until the arc-shaped portion of the slot 216 is opposite the button 212 allowing the front 220 to be pivoted forwardly about the button 214 as a pivot until the clockwise ends of the slots 216 meet the buttons 212 to hold the shelf front 220 in its horizontal position.

While the embodiment of the present invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted.

What is claimed is as follows:

l. A refrigerator including an insulated cabinet containinga storage compartment and an evaporator compartment, a refrigerant evaporator in said evaporator compartment, electrically operated fan means for circulating air from said storage compartment into heat transfer relation with said evaporator and back to said storage compartment, liquefying means for supplying liquid refrigerant to and withdrawing evaporated refrigerant from said evaporator, electrical defrost heating means associated with said evaporator, defrost initiating means for disabling said fan means and said liquefying means and energizing said heating means to quickly raise the temperature of said evaporator for a quick defrost cycle, a thermostatically operable snap acting defrost limiter switch associated with said evaporator and connected in series with said heating means and said electrically operated fan means for deenergizing said heating means when defrosting is completed and for delaying the operation of said fan means after the defrost cycle, and means responsive to the operation of said limiter switch for restoring the normal operation of said liquefying means.

2. A refrigerator including an insulated cabinet containing a storage compartment and an evaporator compartment, a refrigerant evaporator in said evaporator compartment, electrically operated fan means for circulating air from said storage compartment into heat transfer relation with said evaporator and back to said storage compartment, liquefying means for supplying liquid refrigerant to and withdrawing evaporated refrigerant from said evaporator, a double throw defrost switch arrangement having one position providing normal operation of said liquefying means and said fan means and a second position for deenergizing said liquefying means and said fan means for defrosting said evaporator, a thermostatic switch means responsive to the temperature of said evaporator and connected in series with said fan means, said thermostatic switch means being calibrated to close and remain closed during normal refrigeration temperatures of said evaporator and to open and remain open during defrosting temperatures of said evaporator to prevent operation of said fan means while said evaporator is at defrosting temperatures.

3. A refrigerator including an insulated cabinet containing a storage compartment and an evaporator compartment, a refrigerant evaporator in said evaporator compartment, electrically operated fan means for circulating air from said storage compartment into heat transfer relation with said evaporator and back to said storage compartment, liquefying means for supplying liquid refrigerant to and withdrawing evaporated refrigerant from said evaporator, an electrical defrosting means for said evaporator, a double throw defrost switch arrangement having one position connecting with said liquefying means and said fan means and disconnecting said defrosting means and having a second position connecting with said defrosting means and disconnecting said liquefying means and said fan means, and a thermostatic switch means responsive to the temperature of said evaporator and connected in series with said fan means and said defrosting means and in parallel with said liquefying means, said thermostatic switch means being calibrated to close and remain closed during normal refrigeration temperatures .7 of said evaporator and to open and remain open during defrosting temperatures of said evaporator to prevent operation of said fan means while said evaporator is at defrosting temperatures.

4. A refrigerator including an insulated cabinet containing a storage compartment and an evaporator compartment, a refrigerant evaporator in said evaporator compartment, electrically operated fan means for circulating air from said storage compartment into heat transfer relation with said evaporator and back to said storage compartment, liquefying means for supplying liquid refrigerant to and withdrawing evaporated refrigerant from said evaporator, defrost initiating means for disabling said fan means and said liquifying means to raise the temperature of said evaporator for a defrost cycle, a thermostatically operable snap-acting switch associated with said evaporator and connected in series with said electrically operated fan means, said snap-acting switch being calibratedt'o close and remain closed during normal refrigeration temperatures of said evaporator and to open and remain open during defrosting temperatures of said evaporator to prevent operation of said fan means while said evaporator is at defrosting temperatures, and means responsive to the operation of said snap-acting switch for restoring the normal operation of said liquefying means.

References Cited in the file of this patent UNITED STATES PATENTS 2,561,276 Hill July 17, 1951 2,561,277 Hill July 17, 1951 2,713,249 Schordine July 19, 1955 2,750,758 Hoye June 19, 1956 2,792,691 Murphy May 21, 1957 2,863,300 Murphy Dec. 9, 1958 

